Nitric oxides (NOx), mainly including nitric oxide (NO) and nitrogen dioxide (NO2), are some of the most toxic pollutants formed during combustion processes. NOx are precursors of both acid precipitation and ozone formation, and play important roles in the environment through acidification, forest damage, smog formation, damage to human health, depletion of the stratospheric ozone layer, and the greenhouse effect. Most NOx emissions come from automobiles, industrial boilers, refineries, and waste incineration plants, etc. Environmental protection and stringent emission limits both require a significant reduction of NOx emissions from stationary combustors.
Various technological approaches have been applied to NOx reduction from stationary sources. The two major categories of NOx control for stationary applications are precombustion control and post-combustion control. Precombustion control technologies include low NOx burner, overfire air (OFA) systems, exhaust gas recirculation (EGR), and more precisely controlled combustion parameters. Post-combustion treatments include aftertreatment technologies, such as selective catalytic reduction (SCR), selective noncatalytic reduction (SNCR), reburning, and the combination of these aftertreatment technologies.
Magnesia- and alumina-supported ruthenium catalysts have been reported for use in the selective catalytic reduction of nitric oxide with hydrogen. See, “On The Mechanism Of The Selective Catalytic Reduction Of NO to N2 By H2 over Ru/MgO and Ru/Al2O3”, A Hornung et al, Topics in Catalysis, 11/12 (2000) 263-270.
Accordingly, a need exists to improve on the methods and apparatus that are employed for SCR in order to provide a SCR system that results in more efficient NOx removal.